Why the Texas Grid May Need a Coal Plant to Keep Running This Winter

October 1, 2012 | 1:00 PM

Update: On October 30, ERCOT announced that they will not need to keep the coal power units running this winter for transmission and system reliability.

After a coal power plant said they’ll be shutting down some of their units over the winter, the group behind the Texas grid announced last week that it may pay them to keep running anyways.

But that group, the Electric Reliability Council of Texas (ERCOT), insists it’s not because the grid needs to “keep the lights on” for demand reasons. It’s because the transmission lines used by those coal power plants need to have a certain amount of juice running through them, or the grid won’t work correctly.

“The whole purpose of the transmission system is to get power from power plants to consumer loads,” explains Dan Woodfin, ERCOT’s Director of Grid Operations. “When a generator shuts down, that changes the power flows on that transmission system. So we have to make sure that we can get power from the remaining power plants to higher loads.”

The power units in question belong to Luminant, which announced a few weeks ago they’d be idling two of their units at their Monticello coal plant in Northeast Texas during the winter. (The same units Luminant had threatened to shut down last year because of an Environmental Protection Agency rule). ”With power prices very low, those two units are not economical to run during these low demand seasons,” Allan Koenig, vice president of communications for Energy Future Holdings, the parent company for Luminant.

“There will be no impact to our workforce at Monticello,” Koenig says of the planned shutdowns. “We’ll use those workers that operate the plant to do other jobs and maintenance to get ready for the peak demand season that begins in Spring 2013,” Koenig says.

These are large coal units that typically provided a base load of power to the grid, running 24-7. “If you take them offline for a long period of time, you have to make sure the grid stays balanced,” Koenig says.

There are several options for dealing with the transmission issues. Woodfin says its entirely possible they won’t need to keep the units running. If they do make Luminant keep them going, it would be an “incremental” cost, according to Woodfin, spread out among customers in the ERCOT system, and would mostly cover Luminant’s costs, but not pay them market rates.

It’s all at a very preliminary stage at this point. ERCOT will take the next month and look into the issue, and has about sixty days until they have to make a final decision. But it would be fairly unique if they did. Typically, these orders to keep running are made for smaller natural gas plants, not bigger base load coal plants.